1. Field of the Invention
The present invention relates to the use of a combination of natural preservatives such as Natamycin together with Nisin in foodstuffs such as beverages, including beverages which contain tea solids, meats, dressings, sauces, marinades, condiments, spreads, margarine, dairy based foods and the like. The foodstuffs under some conditions are subject to microbial spoilage.
"Food preservation", as that term is used herein, includes methods which guard against food poisoning as well as methods which delay or prevent food spoilage due to microbes. Food preservation keeps food safe for consumption and inhibits or prevents nutrient deterioration or organoleptic changes causing food to become less palatable.
"Food spoilage", as that term is used herein, includes any alteration in the condition of food which makes it less palatable including changes in taste, smell, texture or appearance. Spoiled food may or may not be toxic.
Prevention of food spoilage has been attempted throughout history often through trial and error. The early attempts have resulted in the adoption of such food preservation methods as the drying, salting and/or smoking of foods in order to preserve them. It has been relatively recent in recorded history that food preservation has been placed upon a scientific foundation.
Present food technologists utilize an array of physical, chemical, and biological processes and agents to preserve food and prevent the transmission of disease via foodstuffs. Many chemical agents exist. These agents include antioxidants to prevent chemical degradation of food, as well as compositions which kill or inhibit deleterious bacteria and/or other microbes thereby preserving food i.e. preventing both spoilage and the transmission of disease.
Of rising concern in the food processing industry is yeast, mold and bacterial spoilage of various foods such as wieners, other sausages, cheese, dairy products including novelty ice cream, beverages, dressings, spreads, margarine and seafood. Of particular concern is evidence that pasteurized and fully cooked processed foods are being contaminated with microbes following cooking or pasteurization and prior to packaging for point of sale.
Food preservation by inhibition of growth of yeasts, molds and lactobacilli is often difficult. Unfortunately, microorganism contamination may occur following pasteurization by the processor. Acidified and native pH salad dressings, sauces, marinades, spreads, margarines and other dairy based foods and beverages in the 2.0 to 7.0 pH range are known to be susceptible to spoilage by yeast, mold, acid tolerant bacteria (e.g. Lactobacillus sp., Gluconobacter/Acetobactersp.) and/or mesophilic or thermophilic spore forming (e.g. B. coagulans) and non-spore forming bacteria.
Many people eat processed foods after a significant period of time has elapsed from a first cooking or pasteurization by the food manufacturer thereby permitting bacteria introduced by post-pasteurization contamination to grow. Since this food consumption may occur without reheating the processed food to sufficient temperatures for sufficient time to kill any microbes which may have been introduced subsequent to initial cooking, there is a risk of food spoilage. The present invention seeks to ameliorate the aforementioned risk.
2. Related Art
Natamycin, also known as pimaricin, is an. antifungal agent produced by Streptomyces natalensis. The compound is effective against yeasts and molds and is reported to be ineffective against bacteria. It is approved for use as an additive which may be applied to the surface of cuts and slices of cheese to inhibit mold spoilage (21 CFR 172.155). This information is available from an article on "Antirmicrobials: Assuring Food Safety" by J. Giese in the June 1994 Food Technology periodical 48 (6) pp. 101-110.
Natamycin has been used in animal feeds U.S. Pat. No. 4,600,706, in sausages and sausage casings U.S. Pat. No. 4,664,861 and in mixtures with other preservatives to preserve milk U.S. Pat. No. 5,196,344.
Generally, however, the solubility of Natamycin has limited its use to the surface treatment of cheese for which it is approved by the FDA.
Natamycin has also been of interest in the treatment of food products because it is highly active against yeasts and molds, as opposed to bacteria (see Morris and Hart, "Pimaricin--What Is It?", Culture Dairy Products Journal, Volume 13, page 22, 1987) Reportedly, Natamycin has been applied to food products in several ways. It has been added in dry form to liquids, slurries, pastes and semisolids when adequate mixing can be accomplished, or the pure Natamycin can be mixed with one or more of the dry ingredients and then added to a given food product. Solid foods requiring surface protection can be dipped, misted, fogged or dusted with a solution or suspension of Natamycin. Additionally, it has been suggested that protection from yeast and molds may be achieved in solid food by incorporating Natamycin homogeneously into the food itself.
Natamycin has also been used to retard spoilage of dressed poultry, to protect cottage cheese, and has been widely used in the dip-treatment of cheeses to coat them with the fungicide which is absorbed slightly, and dries to form a solid, surface coating. Various other reports suggest that Natamycin is effective in the treatment of fresh berries, tomatoes, strawberries and raspberries. These reports indicate that Natamycin has an antiyeast activity when added to wines, and various fruit juices, such as apple juice or orange juice. (See, Morris and Hart, cited above.)
Nisin is a natural antimicrobial material which is a polypeptide bacteriocin produced by the lactic acid bacteria, Streptococcus lactis, Group N. Nisin has been used in conjunction with chelating or sequestering agents in the preservation of foodstuffs. U.S. Pat. Nos. 5,573,797; 5,573,800 and 5,573,801 all use this combination as a food preservative.